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Pi Mensae, HD39091, HIP26394

Pi Mensae is a white to yellow subgiant star that can be located in the constellation of Mensa. Pi Mensae is the brightest star in Mensa based on the Hipparcos 2007 apparent magnitude. The star can be seen with the naked eye, that is, you don't need a telescope/binoculars to see it. The star has an estimated age of 3.50 Billion of Years but could be as young as 0.50 to 5.50 according to Hipparcos.

Pi Mensae is the Bayer Classification for the star. HIP26394 is the reference name for the star in the Hipparcos Star Catalogue. The Id of the star in the Henry Draper catalogue is HD39091. Pi Mensae has at least 1 Extrasolar Planets believed to be in orbit around the star.

Location of Pi Mensae

The location of the star in the galaxy is determined by the Right Ascension (R.A.) and Declination (Dec.), these are equivalent to the Longitude and Latitude on the Earth. The Right Ascension is how far expressed in time (hh:mm:ss) the star is along the celestial equator. If the R.A. is positive then its eastwards. The Declination is how far north or south the star is compared to the celestial equator and is expressed in degrees. For Pi Mensae, the location is 05h 37m 08.79 and -80d28`18.0 .

Proper Motion of Pi Mensae

All stars like planets orbit round a central spot, in the case of planets, its the central star such as the Sun. In the case of a star, its the galactic centre. The constellations that we see today will be different than they were 50,000 years ago or 50,000 years from now. Proper Motion details the movements of these stars and are measured in milliarcseconds. The star is moving 1,050.38 ± 0.20 miliarcseconds/year towards the north and 312.01 ± 0.21 miliarcseconds/year east if we saw them in the horizon.

Physical Properties (Colour, Temperature, Metallicity, Age, Mass, Radius) of Pi Mensae

Pi Mensae has a spectral type of G3IV. This means the star is a white to yellow subgiant star. The star is 7394.00000000 Parsecs from the Galactic Centre or terms of Light Years is 24116.5176553600000000s. The star has a B-V Colour Index of 0.6 which means the star's temperature has been calculated using information from Morgans @ Uni.edu at being 5,895 Kelvin.

Pi Mensae Radius has been calculated as being 1.21 times bigger than the Sun.The Sun's radius is 695,800km, therefore the star's radius is an estimated 840,189.99.km. However with the 2007 release of updated Hipparcos files, the radius is now calculated at being round 1.21. The figure is derived at by using the formula from SDSS and has been known to produce widely incorrect figures. The star's solar mass is 1.10 times that of the Sun's. The Sun's Mass is 1,989,100,000,000,000,000,000 billion kg. which to calculate using this website is too large. To give idea of size, the Sun is 99.86% the mass of the solar system.

The star's metallicity is 0.090000, this value is the fractional amount of the star that is not Hydrogen (X) or Helium (Y). An older star would have a high metallicity whereas a new star would have a lower one.

The stars age according to Hipparcos data files put the star at an age of about 3.50 Billion years old but could be between 0.50 and 5.50 Billion years old. In comparison, the Sun's age is about 4.6 Billion Years Old.

Pi Mensae Apparent and Absolute Magnitudes

Pi Mensae has an apparent magnitude of 5.65 which is how bright we see the star from Earth. Apparent Magnitude is also known as Visual Magnitude. If you used the 1997 Parallax value, you would get an absolute magnitude of 4.35 If you used the 2007 Parallax value, you would get an absolute magnitude of 4.34. Magnitude, whether it be apparent/visual or absolute magnitude is measured by a number, the smaller the number, the brighter the Star is. Our own Sun is the brightest star and therefore has the lowest of all magnitudes, -26.74. A faint star will have a high number.

Distance to Pi Mensae

Using the original Hipparcos data that was released in 1997, the parallax to the star was given as 54.92 which gave the calculated distance to Pi Mensae as 59.39 light years away from Earth or 18.21 parsecs. It would take a spaceship travelling at the speed of light, 59.39 years to get there. We don't have the technology or spaceship that can carry people over that distance yet.

In 2007, Hipparcos data was revised with a new parallax of 54.60 which put Pi Mensae at a distance of 59.74 light years or 18.32 parsecs. It should not be taken as though the star is moving closer or further away from us. It is purely that the distance was recalculated.

The star's Galacto-Centric Distance is 7,394.00 Parsecs or 24,116.52 Light Years. The Galacto-Centric Distance is the distance from the star to the Centre of the Galaxy which is Sagittarius A*.

Source of Information

The source of the information if it has a Hip I.D. is from Simbad, the Hipparcos data library based at the University at Strasbourg, France. Hipparcos was a E.S.A. satellite operation launched in 1989 for four years. The items in red are values that I've calculated so they could well be wrong. Information regarding Metallicity and/or Mass is from the E.U. Exoplanets. The information was obtained as of 12th Feb 2017.

Pi Mensae Facts

Alternative Names

Bayer DesignationPi Mensae
Hipparcos Library I.D.26394
Henry Draper Designation39091

Visual Facts

Star Typesubgiant star
Age3.50 Billion Years Old
Age Range0.50 - 5.50 Billion Years Old
Metalicity0.0900
Absolute Magnitude4.35 / 4.34
Visual / Apparent Magnitude5.65
Naked Eye VisibleYes - Magnitudes
Right Ascension (R.A.)05h 37m 08.79
Declination (Dec.)-80d28`18.0
Galactic Latitude-29.78 degrees
Galactic Longitude292.52 degrees
1997 Distance from Earth54.92 Parallax (milliarcseconds)
 59.39 Light Years
 18.21 Parsecs
2007 Revised Distance from Earth54.60 Parallax (milliarcseconds)
 59.74 Light Years
 18.32 Parsecs
Galacto-Centric Distance24,116.52 Light Years / 7,394.00 Parsecs
Proper Motion Dec.1050.38 ± 0.20 milliarcseconds/year
Proper Motion RA.312.01 ± 0.21 milliarcseconds/year
B-V Index0.60
Radial Velocity10.90 ± 0.74 km/s
Iron Abundance0.07 ± 0.01 Fe/H
Spectral TypeG3IV
Colour(G) White to Yellow

Companions (Multi-Star and Exoplanets) Facts

Exoplanet Count1

Estimated Facts

Calculated Effective Temperature5,895 Kelvin
Mass Compared to the Sun1.10
Metallicity0.09000

Sources and Links

SIMBAD SourceLink

Related Stars


List of Extrasolar Planets orbiting Pi Mensae


NameStatusMass (Jupiters)Orbital Period (Days)EccentricityDiscoveredSemi-Major AxisPeriastron
Hd 39091 BConfirmed10.32049.0000.6120013.28330.000

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